mybatis的typeHandler
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2022-04-24 10:12:28
typeHandler作用： 1.传参时将javaType类型转换成jdbcType 2.结果集中ResultSet中取值时，jdbcType转换为javaType; 系统自定义的typeHandler: mybatis系统内部定义了一系列的typeHandler；基本涵盖了我们正常使用的类型转换； ......
typehandler作用：
1.传参时将javatype类型转换成jdbctype
2.结果集中resultset中取值时，jdbctype转换为javatype;
系统自定义的typehandler:
mybatis系统内部定义了一系列的typehandler；基本涵盖了我们正常使用的类型转换；如下
选取一个系统自定义的typehandler看看；
在包org.apache.ibatis.type下有一个stringtypehandler.java
源码如下：
public class stringtypehandler extends basetypehandler<string> {
@override
public void setnonnullparameter(preparedstatement ps, int i, string parameter, jdbctype jdbctype)
throws sqlexception {
ps.setstring(i, parameter);
}
@override
public string getnullableresult(resultset rs, string columnname)
throws sqlexception {
return rs.getstring(columnname);
}
@override
public string getnullableresult(resultset rs, int columnindex)
throws sqlexception {
return rs.getstring(columnindex);
}
@override
public string getnullableresult(callablestatement cs, int columnindex)
throws sqlexception {
return cs.getstring(columnindex);
}
}
stringtypehandler继承了basetypehandler;而basetypehandler实现了接口typehandler,
basetypehandler中代码
/**
* copyright 2009-2015 the original author or authors.
*
* licensed under the apache license, version 2.0 (the "license");
* you may not use this file except in compliance with the license.
* you may obtain a copy of the license at
*
* http://www.apache.org/licenses/license-2.0
*
* unless required by applicable law or agreed to in writing, software
* distributed under the license is distributed on an "as is" basis,
* without warranties or conditions of any kind, either express or implied.
* see the license for the specific language governing permissions and
* limitations under the license.
*/
package org.apache.ibatis.type;
import java.sql.callablestatement;
import java.sql.preparedstatement;
import java.sql.resultset;
import java.sql.sqlexception;
import org.apache.ibatis.executor.result.resultmapexception;
import org.apache.ibatis.session.configuration;
/**
* @author clinton begin
* @author simone tripodi
*/
public abstract class basetypehandler<t> extends typereference<t> implements typehandler<t> {
protected configuration configuration;
public void setconfiguration(configuration c) {
this.configuration = c;
}
@override
public void setparameter(preparedstatement ps, int i, t parameter, jdbctype jdbctype) throws sqlexception {
if (parameter == null) {
if (jdbctype == null) {
throw new typeexception("jdbc requires that the jdbctype must be specified for all nullable parameters.");
}
try {
ps.setnull(i, jdbctype.type_code);
} catch (sqlexception e) {
throw new typeexception("error setting null for parameter #" + i + " with jdbctype " + jdbctype + " . " +
"try setting a different jdbctype for this parameter or a different jdbctypefornull configuration property. " +
"cause: " + e, e);
}
} else {
try {
setnonnullparameter(ps, i, parameter, jdbctype);
} catch (exception e) {
throw new typeexception("error setting non null for parameter #" + i + " with jdbctype " + jdbctype + " . " +
"try setting a different jdbctype for this parameter or a different configuration property. " +
"cause: " + e, e);
}
}
}
@override
public t getresult(resultset rs, string columnname) throws sqlexception {
t result;
try {
result = getnullableresult(rs, columnname);
} catch (exception e) {
throw new resultmapexception("error attempting to get column '" + columnname + "' from result set. cause: " + e, e);
}
if (rs.wasnull()) {
return null;
} else {
return result;
}
}
@override
public t getresult(resultset rs, int columnindex) throws sqlexception {
t result;
try {
result = getnullableresult(rs, columnindex);
} catch (exception e) {
throw new resultmapexception("error attempting to get column #" + columnindex+ " from result set. cause: " + e, e);
}
if (rs.wasnull()) {
return null;
} else {
return result;
}
}
@override
public t getresult(callablestatement cs, int columnindex) throws sqlexception {
t result;
try {
result = getnullableresult(cs, columnindex);
} catch (exception e) {
throw new resultmapexception("error attempting to get column #" + columnindex+ " from callable statement. cause: " + e, e);
}
if (cs.wasnull()) {
return null;
} else {
return result;
}
}
public abstract void setnonnullparameter(preparedstatement ps, int i, t parameter, jdbctype jdbctype) throws sqlexception;
public abstract t getnullableresult(resultset rs, string columnname) throws sqlexception;
public abstract t getnullableresult(resultset rs, int columnindex) throws sqlexception;
public abstract t getnullableresult(callablestatement cs, int columnindex) throws sqlexception;
}
getresult分别用columnname和columnindex从resultset中获取数据，callablestatement表示从存储过程中获取结果及数据的方法；
下面我们创建自定义typehandler
rolemapper.java
package com.learn.charter2.mapper;
import java.util.list;
import com.learn.charter2.po.role;
public interface rolemapper {
role getrole(long id) throws exception;
int deleterole(long id) throws exception;
int insertrole(role role) throws exception;
list<role> findrole(role role) throws exception;
}
role.java
package com.learn.charter2.po;
public class role {
private long id;
private string rolename;
private string note;
private integer pk;
public long getid() {
return id;
}
public void setid(long id) {
this.id = id;
}
public string getrolename() {
return rolename;
}
public void setrolename(string rolename) {
this.rolename = rolename;
}
public string getnote() {
return note;
}
public void setnote(string note) {
this.note = note;
}
public integer getpk() {
return pk;
}
public void setpk(integer pk) {
this.pk = pk;
}
}
sqlsessionfactoryutil.java
package com.learn.charter2.util;
import java.io.inputstream;
import java.util.logging.level;
import java.util.logging.logger;
import org.apache.ibatis.io.resources;
import org.apache.ibatis.session.sqlsession;
import org.apache.ibatis.session.sqlsessionfactory;
import org.apache.ibatis.session.sqlsessionfactorybuilder;
public class sqlsessionfactoryutil {
private static sqlsessionfactory sqlsessionfactory=null;
private static final class class_lock=sqlsessionfactoryutil.class;
private sqlsessionfactoryutil() {
}
public static sqlsessionfactory initsqlsessionfactory(){
string resource="mybatis-config.xml";
inputstream inputstream=null;
try {
inputstream=resources.getresourceasstream(resource);
} catch (exception e) {
logger.getlogger(sqlsessionfactoryutil.class.getname()).log(level.severe,null,e);
}
synchronized (class_lock) {
if(sqlsessionfactory==null){
sqlsessionfactory=new sqlsessionfactorybuilder().build(inputstream);
}
}
return sqlsessionfactory;
}
public static sqlsession opensqlsession(){
if(sqlsessionfactory==null){
initsqlsessionfactory();
}
return sqlsessionfactory.opensession();
}
}
log4j.properties
log4j.rootlogger=debug,stdout log4j.logger.org.mybatis=debug log4j.appender.stdout=org.apache.log4j.consoleappender log4j.appender.stdout.layout=org.apache.log4j.patternlayout log4j.appender.stdout.layout.conversionpattern=%5p %d %c:%m%n
mybatis-config.xml
1 <?xml version="1.0" encoding="utf-8" ?> <!doctype configuration public "-//mybatis.org//dtd config 3.0//en" "http://mybatis.org/dtd/mybatis-3-config.dtd"> 2 <configuration> 3 <typehandlers> 4 <typehandler handler="com.learn.charter2.util.mystringtypehandler" javatype="string" jdbctype="varchar"/> 5 <typehandler handler="com.learn.charter2.util.myintergertypehandler" javatype="int" jdbctype="varchar"/> 6 </typehandlers> 7 <environments default="development"> 8 <environment id="development"> 9 <transactionmanager type="jdbc"> 10 <property name="autocommit" value="false" /> 11 </transactionmanager> 12 <datasource type="pooled"> 13 <property name="driver" value="com.mysql.jdbc.driver" /> 14 <property name="url" value="jdbc:mysql://localhost:3306/mybatis" /> 15 <property name="username" value="root" /> 16 <property name="password" value="gys" /> 17 </datasource> 18 </environment> 19 </environments> 20 <mappers> 21 <mapper resource="com/learn/charter2/mapper/rolemapper.xml" /> 22 </mappers> 23 </configuration>
rolemapper.xml
1 <?xml version="1.0" encoding="utf-8" ?> <!doctype mapper public "-//mybatis.org//dtd mapper 3.0//en" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
2 <mapper namespace="com.learn.charter2.mapper.rolemapper">
3
4 <resultmap type="com.learn.charter2.po.role" id="rolemap">
5 <id column="id" property="id" javatype="long" jdbctype="bigint"/>
6 <result column="role_name" property="rolename" javatype="string" jdbctype="varchar"/>
7 <result column="note" property="note" typehandler="com.learn.charter2.util.mystringtypehandler"/>
8 <result column="pk" property="pk" typehandler="com.learn.charter2.util.myintergertypehandler"/>
9 </resultmap>
10
11
12 <select id="getrole" parametertype="long" resultmap="rolemap">
13 select id,role_name as rolename,note from t_role where id=#{id}
14 </select>
15
16 <select id="findrole" parametertype="com.learn.charter2.po.role" resultmap="rolemap">
17 select id,role_name as rolename,note,pk from t_role
18 <where>
19 <if test="rolename !=null">
20 role_name like concat('%',#{rolename,javatype=string,jdbctype=varchar,typehandler=com.learn.charter2.util.mystringtypehandler},'%')
21 </if>
22 <if test="pk !=null">
23 and pk =#{pk,javatype=int,jdbctype=varchar,typehandler=com.learn.charter2.util.myintergertypehandler}
24 </if>
25 </where>
26
27
28 </select>
29
30 <insert id="insertrole" parametertype="com.learn.charter2.po.role">
31 insert into t_role
32 (role_name,note)
33 values
34 (#{rolename},#{note})
35 </insert>
36 <delete id="deleterole" parametertype="long">
37 delete from t_role where id=#{id}
38 </delete>
39 </mapper>
myintergertypehandler.java
1 package com.learn.charter2.util;
2
3
4 import java.sql.callablestatement;
5 import java.sql.preparedstatement;
6 import java.sql.resultset;
7 import java.sql.sqlexception;
8
9 import org.apache.ibatis.type.jdbctype;
10 import org.apache.ibatis.type.mappedjdbctypes;
11 import org.apache.ibatis.type.mappedtypes;
12 import org.apache.ibatis.type.typehandler;
13 import org.apache.log4j.logger;
14
15 import sun.security.action.getintegeraction;
16
17
18 /**
19 * @mappedtypes({integer.class})
20 @mappedjdbctypes(jdbctype.varchar)
21 *
22 */
23 public class myintergertypehandler implements typehandler<integer> {
24
25 private logger log=logger.getlogger(myintergertypehandler.class);
26
27 private int getint(string v){
28 if("a".equals(v)){
29 return 10;
30 }else if("b".equals(v)){
31 return 20;
32 }else if("c".equals(v)){
33 return 30;
34 }else{
35 return 60;
36 }
37 }
38 @override
39 public integer getresult(callablestatement cs, int index)
40 throws sqlexception {
41 log.info("使用我的integertypehandler,callblestatment下表获取字符串");
42 return getint(cs.getstring(index));
43 }
44
45 @override
46 public integer getresult(resultset rs, int index) throws sqlexception {
47 log.info("使用我的integertypehandler,resultset下标获取字符串");
48 return getint(rs.getstring(index));
49 }
50
51 @override
52 public integer getresult(resultset rs, string colname) throws sqlexception {
53 log.info("使用我的integertypehandler,resultset 列名获取字符串");
54 return getint(rs.getstring(colname));
55 }
56
57 @override
58 public void setparameter(preparedstatement ps, int index, integer value,jdbctype jt) throws sqlexception {
59 log.info("使用我的integertypehandler==index:"+index+";value:"+value);
60 string v="";
61 if(value==1){
62 v="a";
63 }else if(value==2){
64 v="b";
65 }else if(value==3){
66 v="c";
67 }else {
68 v="guoyansi";
69 }
70 ps.setstring(index, v);
71 }
72 }
mystringtypehandler.java
1 package com.learn.charter2.util;
2
3
4 import java.sql.callablestatement;
5 import java.sql.preparedstatement;
6 import java.sql.resultset;
7 import java.sql.sqlexception;
8
9 import org.apache.ibatis.type.jdbctype;
10 import org.apache.ibatis.type.mappedjdbctypes;
11 import org.apache.ibatis.type.mappedtypes;
12 import org.apache.ibatis.type.typehandler;
13 import org.apache.log4j.logger;
14
15
16 @mappedtypes({string.class})
17 @mappedjdbctypes(jdbctype.integer)
18 public class mystringtypehandler implements typehandler<string> {
19 private logger log=logger.getlogger(mystringtypehandler.class);
20
21 @override
22 public string getresult(callablestatement cs, int index)
23 throws sqlexception {
24 log.info("使用我的stringtypehandler,callblestatment下表获取字符串");
25 return cs.getstring(index);
26 }
27
28 @override
29 public string getresult(resultset rs, int index) throws sqlexception {
30 log.info("使用我的stringtypehandler,resultset下标获取字符串");
31 return rs.getstring(index);
32 }
33
34 @override
35 public string getresult(resultset rs, string colname) throws sqlexception {
36 log.info("使用我的stringtypehandler,resultset 列名获取字符串");
37 return rs.getstring(colname);
38 }
39
40 @override
41 public void setparameter(preparedstatement ps, int index, string value,
42 jdbctype jt) throws sqlexception {
43 value=value+"m";
44 log.info("使用我的stringtypehandler==index:"+index+";value:"+value);
45 ps.setstring(index, value);
46 }
47
48
49 }
charter2main.java
1 package com.learn.charter2.main;
2
3 import java.util.list;
4
5 import org.apache.ibatis.session.sqlsession;
6
7 import com.learn.charter2.mapper.rolemapper;
8 import com.learn.charter2.po.role;
9 import com.learn.charter2.util.sqlsessionfactoryutil;
10
11 public class charter2main {
12 public static void main(string[] args) {
13 sqlsession sqlsession = null;
14 try {
15 sqlsession = sqlsessionfactoryutil.opensqlsession();
16 rolemapper rolemapper = sqlsession.getmapper(rolemapper.class);
17 role role = new role();
18 role.setpk(10);
19 list<role> list=rolemapper.findrole(role);
20 for(role r:list){
21 system.out.println("id:"+r.getid()+";rolename:"+r.getrolename()+";note:"+r.getnote()+";pk:"+r.getpk());
22 }
23 } catch (exception e) {
24 system.err.println(e.getmessage());
25 sqlsession.rollback();
26 }finally{
27 if(sqlsession!=null){
28 sqlsession.close();
29 }
30 }
31 }
32
33 }
自定义typehandler的三个步骤：
1.定义typehandler(myintergertypehandler.java mystringtypehandler.java)
2.配置typehandler(mybatis-config.xml中3-6行)
3.指定入参中哪个字段使用typehandler(mapper.xml中19-24行)
4.指定出参中哪个字段使用typehandler(mapper.xml中7-8行)
以myintergertypehandler为例，运行一下charter2main.java
charter2main 中传入的pk参数是10，被typehandler默默的转换成了guoyansi;
因为guoyansi在数据库中找到了值，在被返回到java中，guoyansi又被typehandler转化成了60；
这个例子展示的就是integer和string之间的转换。